Thus, upregulation of PLK3 might lead to downregulation of CDC25C and CHEK1. Additionally, CHEK1 is deleted in 6.8% of non-seminomas, suggesting that deletion of CHEK1 might be of benefit for efficacy of a CDK4/6 inhibitor treatment in non-seminomas (Supplementary data S1A). Here, CDK4 is linked to seminoma.